“Even if we're happy about it, it's the Salafists who have carried it out," Shalom said, in reference to extremist Sunni Muslim groups who oppose the Shiite, Iran-backed Hezbollah.

"It's a harsh blow for Hezbollah, which has tried to present the assassination (as Israeli) in order to distract from internal wrangling and divisions in Lebanon brought on by the Syrian" civil war, Shalom said.

The slain leader, Hassan Hawlo al-Lakiss, was the most senior Hezbollah figure to be assassinated since Imad Mughniyeh was killed in a Damascus bombing in 2008, which the group also blamed on Israel.

Both men were part of Hezbollah's secretive top leadership.

Hezbollah on Wednesday said al-Lakiss had been assassinated near Beirut. “The Islamic resistance announces the death of one of its leaders, the martyr Hassan Hawlo al-Lakiss, who was assassinated near his house in the Hadath region" east of Beirut, Hezbollah television channel Al Manar said.

"Direct accusation is aimed of course against the Israeli enemy which had tried to eliminate our martyred brother again and again and in several places but had failed, until yesterday evening," a Hezbollah statement broadcast by the channel said.

“This enemy must bear full responsibility for and all the consequences of this heinous crime," it added.

A Hezbollah source said Lakiss was very close to the Shiite movement's leader, Hassan Nasrallah.

The killing occurred around midnight, soon after Nasrallah had given an interview to Lebanese broadcaster OTV.

It should be noted that Hezbollah has been facing a furious slew of attacks by forces inside Lebanon in recent months.

A series of car bomb explosions and other attacks targeting Hezbollah are believed to have been carried out by supporters of the rebel forces in Syria, where Hezbollah is siding with the Assad regime in an extremely cruel three-year civil war.